This invention relates to wastewater treatment systems, and more particularly to a system having a vessel or tank with integral treatment and settling chambers.
In a common type of wastewater treatment system, wastewater is treated by aeration in a first tank. Wastewater from this treatment or aeration tank is delivered to a second tank where settling of sludge components is allowed to occur. A lower end of this settling or clarification tank is connected to a lower end of the aeration or treatment tank.
U.S. Pat. Nos. 5,766,459 and 5,830,351 to Carl E. Adams, Jr., disclose such an activated sludge system wherein the clarification and aeration tanks are chambers in the same vessel. The chambers are defined or separated by an inclined baffle plate so that the clarification chamber tapers in a downward direction to funnel the sludge towards an opening or gap at the lower end of the baffle. The sludge moves through the gap into a lower region of the aeration chamber, propelled in part by a recycle pump which draws wastewater from the aeration chamber and delivers the wastewater to the upper surface of a cylindrical or rectangular well located at the upper end of the clarification chamber. The center well serves to direct the delivered recycled wastewater in a downward direction through the clarification chamber.
In particular embodiments of these integral wastewater treatment systems, the baffle and consequently the clarification chamber may have a conical or rectangular configuration. The clarification chamber tapers at its base to a narrow throat where the sludge reenters the aeration chamber. In certain configurations, it has been noticed that the gap extending between the narrow throat at the base of the clarification chamber and the lower region of the aeration chamber, although narrow and designed to maintain a downward and outward velocity, permits miscellaneous and unpredictable backmixing generating of undesirable upward currents into the clarification chamber. These upward currents interfere with an even distribution of the returning or settling sludge in the clarification chamber and, in some cases, cause a bridging or accumulation of sludge at the base of the clarification chamber. The bridging in turn can result in floating sludge on the surface of the clarification pool. Although the floating sludge does not impair proper operation of the wastewater treatment system, that phenomenon does present an aesthetic drawback.